Method and apparatus for forming a honeycomb-shaped core for honeycomb panels

ABSTRACT

A core has honeycomb-shaped cells in rows with sides adhered to each other by glue. All the glue adhering all the cells of at least one of the rows to the cells of a next of the rows is in two glue strips that are spaced from each other.

BACKGROUND OF THE INVENTION

The invention relates to a method for forming a honeycomb-shaped core,which is suitable for being included in a honeycomb panel for example,wherein webs or plates of deformable material, in particular cellulosematerial such as, for example, paper or cardboard, are provided with anumber of parallel glue strips and then bonded onto each other andpressed, wherein the glue strips for two plates which possibly originatefrom said webs, to be successively mounted onto each other, are disposedin a laterally mutually staggered manner, in order to enable theformation of honeycomb cells when the strips which are cut from a numberof plates glued to one another are pulled off each other. Generally, forreasons of efficiency, the honeycomb cells have adhering sides which aresmaller than the bridging sides of the cells which extend between theplates or strips.

If a large number of plates, for instance 200, are bonded to one anotherin a stack in this manner, this stack is pressed together and is thencut into transverse bands. These stacks of bands each form a honeycombcore, which, after having been drawn out can, for example, be includedin the inner door of a house.

Applying the glue, such as potato starch glue, takes place in a coldstate with the help of glue rollers which rotate through a glue bath andtransfer the desired quantity of glue onto the plate led past. The glueroller is provided with ribs extending in circumferential direction,which are spaced at a distance from one another which corresponds to thedesired lateral distance between the glue strips which are to be appliedto the plate.

Applying glue strips preferably takes place in such a way that for twoplates which originate or otherwise from respective webs and which areto be mounted onto each other, the glue strips of the one plate will bedisposed in a laterally staggered manner with respect to the glue stripsof the other plate. This is achieved either by shifting successiveplates laterally over the desired mutual distance, use being made of astationary glue roller, or by using two glue rollers mounted in parallelprocessing paths or consecutively in one processing path, the ribs orcomparable glue contact means of which being arranged over that distancein a laterally mutually displaced manner.

When carrying out the known method it has appeared that glue remains onthe ribs or comparable means and on the glue roller, owing to which theglue contact area with the webs or the plates increases in the course oftime, so that the glue strips get wider and/or more irregular. If thisis to be avoided, then regular cleaning of the glue rollers isnecessary, which entails a loss of production time and increases labourcosts.

The glue strips have a lateral dimension such that they glue successiveplates onto each other along the complete adhering sides of thehexagonal cells, for instance with a dimension of 12 mm for honeycombcells having a distance between opposite adhering sides of 25 to 37 mmin the honeycomb core to be formed. As a consequence of the manner ofapplying the glue, the glue strips are, however, irregular and the widththereof varies within a range of 10-17 mm. Because of this the cells toowill be irregularly shaped and more plate material will be needed for ahoneycomb having a desired length dimension. Because of the gluesticking to the ribs, successive plates and the strips cut from themwill be adhered to one another over larger areas in a stack, forming ahoneycomb core, as a result of which the achievable stretched a lengthof that stack will be reduced and the efficiency will consequently bedecreased. Moreover, glue is spilled.

SUMMARY OF THE INVENTION

An object of the invention is to provide a method of the kind mentionedin the preamble, with which the glueing and production process for thehoneycomb core is controlled in a better way.

According to the invention for this purpose glue strips are applied withthe help of glue spout nozzles. By applying glue by means of glue spoutnozzles an accumulation of glue remains on glue supplying surfaces isavoided, which would lead to enlargement of the contact surface andcould result in irregularly glued surfaces of the plates. The glue isdosed in accurately controlled quantities through an opening of thespout nozzles which is at least almost directly in contact with theplate material. With the glue spout nozzles glue can be dispensed in aconstant, regular way.

According to a further development of the method of the invention gluestrips are applied, each of which is composed of two transverselymutually spaced glue tracks. Their edges facing away from each other arespaced at a distance in the order of magnitude of the adhering side of ahoneycomb cell to be formed. The so-called glue strips are thus reducedto areas which are really necessary to realize honeycomb cells in thehoneycomb core to be formed. As a result successive plates are onlyadhered to one another at the position of the areas adjacent the desiredcorners of the cells, which suffices for the formation of honeycombcells when the bands in said stacks are to some extent pulled away fromeach other.

If obtaining regular-hexagonal honeycomb cells in the honeycomb core isdesired, it is preferable that the distance between two laterallyadjacent glue tracks, of which the one is applied on the one plate andthe other on the plate to be placed thereon, at least almost correspondsto the desired bridging side of a honeycomb cell.

The glue tracks are arranged on a plate preferably at a centre-to-centredistance of approximately 7 to 8 mm from each other. Then, the width ofthe glue tracks can be limited to approximately 2 to 4 mm in lateraldirection. The height can be 1 mm or even less.

As a result of the reduced use of glue a lower water content of theglued plates than was the case up until now is also achieved. Forexample, paper usually has a water content of approximately 8%, thepotato starch glue has a water content of approximately 80% and theglued plate stack has a water content of approximately 14-18%. Becauseof the reduced size of the glue tracks according to the invention, awater content of the glued plate stack is achieved which does not exceed10-12%. Owing to this the plates are less susceptible to irreversibledeformation and breakage than was the case up until now and they needless drying. When glueing plates for honeycomb cores many glue tracks,possibly as many as 60, have to be appplied adjacent one another. Theapparatus for use when carrying out the method according to theinvention comprises for that purpose a glue station which is to belocated above the plates or webs for use in the honeycomb cell and has aseries of glue spout nozzles arranged laterally adjacent one another anda primary glue supply means therefor, in which the glue spout nozzlesare connected to the primary glue supply means in groups via secondaryglue supply means, in which the secondary glue supply means are providedwith selectively operable valves for passing glue or otherwise, withwhich adjustment can be made to changed plate widths. The primary gluesupply means is preferably provided with a selectively operable gluepressure regulator.

In addition, it is preferable if means are available for measuring thevelocity of the plates led past the glue station, the glue pressureregulator being operable in response to the measuring data of thevelocity measuring means. Thus, the occurrence of too largeirregularities in the size of the glue tracks in the longitudinaldirection thereof as a result of unforeseen (temporary or brief) changesin the plate velocity is avoided.

In addition, it is preferable if, within each group of glue spoutnozzles, the glue spout nozzles are connected to the secondary gluesupply means via tertiary glue supply means, in which the tertiary gluesupply means are formed as a series of glue supply tubes, which areparallely arranged and are at least almost equally dimensioned. By doingso it is ensured that within each group the same glue flow is dispensedby the spout nozzles located therein.

BRIEF DESCRIPTION OF THE DRAWING

The invention will now be described in more detail on the basis of thedetails shown in the accompanying drawings.

FIG. 1 shows a schematic representation of a production process forhoneycomb cores according to the invention;

FIG. 2 shows a schematic cross section of two plates after glue stripshave been applied to the latter in the known manner, the glue patternbeing shown;

FIG. 3 shows a schematic cross section corresponding to that of FIG. 2of two plates which are provided in accordance with the invention withglue tracks and are intended for the formation of a honeycomb core;

FIG. 4 shows a schematic reproduction of a part of the glue stationwhich is used in the method according to the invention; and

FIG. 4A shows a view of a part of the glue station of FIG. 4.

DESCRIPTION OF EMBODIMENTS

In the schematic representation according to FIG. 1 two rollers 1' and1" can be seen, to which webs of paper or cardboard, respectively, arerolled, from which webs the plates for the strips for the honeycomb coreoriginate. The rollers 1' and 1" are arranged parallely and on rotationthey supply paper webs W1 and W2, respectively. The webs W1 and W2 areled past glue stations 3' and 3", respectively, where, via the gluespout nozzles 4' and 4", in a manner corresponding to the invention,thin, parallel glue tracks extending in longitudinal direction of theweb are applied onto the upper surface of the webs W1 and W2. The websW1 and W2 are supported by conveyor belts 5' and 5' and are led by themto first cutting stations 6' and 6", respectively, where the webs W1 andW2, which are provided with the glue tracks, are cut to suitable lengthsto panels WP1 and WP2, respectively.

It will be understood that the glue stations can also be arranged in analternative manner at a location downstream from the cutting stations,in which case the glue tracks will be applied on the plates already cutto length. However, this makes no difference for the method according tothe invention.

The cut panels WP1 and WP2 are supported by conveyor belts 7' and 7",respectively, and then delivered, which is shown in a schematic way witharrows, to subsequent, common conveyor belt 8, such that at every plateWP2 a plate WP1 arrives. These plates WP1 and WP2 are led successivelyand in pairs through a first press roller assembly 9 to conveyor belt10. In addition, the upper press roller is provided with circumferentialgrooves which coincide with the glue tracks on plate WP1, so that thelatter are not disturbed during pressing. The pair of plates WP1 and WP2bonded in this way is then delivered by conveyor belt 10 to a stack S onconveyor belt 11. The stack S consists of a series of plate pairs WP1and WP2. With their lower surface the plates WP2 adhere to the gluetracks which are applied to the upper surface of an underlying plateWP1.

The stack S, if the latter has 200 plates, for instance, is led by theconveyor belt 11 to a second pressing roller assembly 12, where thepairs of plates are firmly adhered to each other by exerting pressure.The resulting compressed stack S' is then led via conveyor belt 13 to asecond cutting station 14, where the stack is held by means not shownduring cutting and is each time moved forward at a suitable pace, in thecourse of which after each cutting action a stack WS of bands bonded toone another is obtained, which stack, when extended, takes the shape ofa honeycomb core.

Apart from the glue stations 3', 3" the schematic representation of FIG.1 is also applicable to known methods for the production of honeycombcores. How the glue pattern according to the prior art will look likefor a honeycomb core to be made with cells with an adhering side of 12mm and a length h₁ (the largest distance between two consecutive plates)of 37 mm, is shown in FIG. 2. In an alternative embodiment the adheringside and the length h₁ are 11 mm and 25 mm, respectively. On the toppaper plate W1 with a thickness of 0,2 mm glue strips 20 are appliedwhich have a nominal width b1 of 11 mm and are spaced at an interspaceb2 of twice a bridging side and once an adhering side, in this case 74mm. On the paper plate W2 (also 0,2 mm thick) glue strips 21 are appliedwhich are likewise 11 mm wide and are spaced at a distance of 74 mm.When the plates W1 and W2 are pressed together, the glue strip willexpand laterally somewhat and the plate W1 will be glued over strips ofapproximately 12 mm in width to the lower side of the plate W1. When theplates W1 and W2 are included in the plate stack, and are then pulledapart in the directions X, the plates W1 and W2 will thus remain gluedto each other at the location of the glue strip, thus over an area of 12mm, and the adjacent parts will rotate relatively in directions T₁ T₂and then form the inclined bridging sides of the honeycomb cells. Thishas been shown schematically in an exaggerated way with broken lines.

In FIG. 3 a representation is given which likens that of FIG. 2, but, inaddition, in accordance with the invention each glue strip is replacedby one pair of glue tracks 30, which have a width b3 of 3 mm and arespaced at an interspacing b4 of 5 mm. The glue tracks of adjacentadhering sides are again at a mutual distance b5 of 74 mm. On the plateW2 similar glue tracks 31 are applied, however in a centrally staggeredmanner. The glue tracks nearest each other in a horizontal sense whichare located at different plates, are at a mutual distance which is equalto the corresponding distance in the glue pattern according to FIG. 2.After pressing the glue tracks are each widened on both sides to 4 mmwide tracks, with an interspacing of 4 mm. When W1 and W2 with the gluepattern of FIG. 3 are pulled away from each other, the same effect isachieved as in FIG. 2. At the location of the glue tracks 31 the platesW1 and W2 are kept attached to each other, the areas located between theglue tracks of successive plates W1 and W2 again forming the inclinedsides of the honeycomb cells. However, this same effect is achieved withmuch less glue.

In FIGS. 4 and 4A a schematic side view is shown of a possibleembodiment of the glue station 3' (and glue station 3", not shown) . Theglue station 3', of which a part which forms a group of glue spoutnozzles is shown here, is arranged above the web W1 which is rolled offroller 1' in the direction shown by the arrow. Downstream from the gluestation 3' the web W1 is supported by a roller 5'.

The glue station 3' is suspended in a fixed frame, not shown, by meansof bars 101 and contains a glue supply tube 100, which leads to adistribution chamber 102. The distribution chamber 102 is provided witha horizontal series of outlets, not shown, which connect to separateglue supply channels 105 feeding glue from the chamber 102 to glue spoutnozzles 4', which are formed in the glue block 103, which is attached insuch a way onto the chamber 102 by means of screw bolts that no glue canleak out.

On the top side of the glue chamber 102 there are closing screws 104,with which the passage opening of the chamber 102 to the glue channel105 concerned can be opened or closed. Because of this, adjustment canbe made to the width of the plates which are being processed.

The web W1 is pushed up somewhat by the roller 5', so that the topsurface of the web W1 abuts the spout nozzle openings with slightpressure. Upstream from there the glue station is provided with a fixedsteel bar 108 for guiding the paper web along the spout nozzles to keepthe contact pressure as minimal as possible.

The roller 1' is provided with an angular velocity meter 120 and asupply meter 121. The data of both of these is delivered via data line122 to control means, not shown, in the glue station 3', which canregulate the supply pressure of the glue in response to those data.

The glue station 3' is composed of a number of the groups shown. Eachgroup can contain 16 glue spout nozzles and can have a width of 420 mm.

On the side the glue group shown in FIG. 4A is provided with aconnection 110 with valve 111, on to which a tube for a cleaning agentcan be connected.

I claim:
 1. A method for forming a honeycomb-shaped core suitable forbeing included in a honeycomb panel, wherein webs or plates ofdeformable material are provided with continuously or otherwiseextending glue strips, wherein, for every two plates or webs to bemounted onto each another, said glue strips are disposed in a laterallyregularly mutually staggered manner on faces thereof having the sameorientation and wherein the plates or webs are pressed onto each otherin order to allow them to adhere to each other locally wherein the gluestrips are applied by means of glue spout nozzles, wherein the gluestrips each comprise two glue tracks which are laterally spaced and arekept spaced with their opposing longitudinal edges at a distance in theorder of magnitude of a width of a side of a honeycomb cell.
 2. Methodaccording to claim 1, wherein the glue tracks of a glue strip are spacedat a lateral intermediate interspacing in the order of magnitude of thewidth of the glue tracks.
 3. Method according to claim 1, wherein thethickness of the glue tracks in a lateral direction is approximately 2to 4 mm.
 4. Method according to claim 1, wherein one of the glue tracksis laid on one plate or web and the other on the plate or web to bepressed thereon.
 5. Method according to claim 1, wherein a plurality ofplates is assembled in a stack, said stack is compressed and is then cutinto a plurality of stacks of bands, wherein each of said tracks isextendable to form a honeycomb core.
 6. Method according to claim 1,wherein the deformable material is a cellulose material.
 7. Methodaccording to claim 6, wherein said cellulose material is a papermaterial.
 8. Method according to claim 6, wherein said cellulosematerial is a cardboard material.
 9. Method according to claim 1 whereinthe glue tracks are applied onto webs, said webs being cut into platesafter being pressed onto each other, consecutive plates being assembledin a stack, said stack being compressed and then cut into a plurality ofstacks of bands, which each are extendable to form a honeycomb core. 10.Apparatus for use for forming a honeycomb-shaped core suitable for beingincluded in a honeycomb panel, said core being composed of an expandedstack of bands of deformable material, said stack of bands being cutfrom a stack of plates of said deformable material, said plates beingadhered to each other by means of glue strips applied on said plates,the apparatus comprising a conveyor for said plates and a glue stationlocated above the conveyor for said plates, said glue station beingprovided with a series of glue spout nozzles arranged laterally adjacentone another and a primary glue supply means therefor, in which the gluespout nozzles are connected to the primary glue supply means in groupsvia secondary glue supply means, in which the secondary glue supplymeans are provided with selectively operable valves for passing glue.11. Apparatus according claim 10, in which the primary glue supply meansis provided with a selectively operable glue pressure regulator. 12.Apparatus according to claim 11, further comprising a means formeasuring the velocity of the plates carried past the glue station,wherein the glue pressure regulator is operable in response to themeasuring data of the velocity measuring means.
 13. Apparatus accordingto claim 11, in which within each group of glue spout nozzles the gluespout nozzles are connected to the secondary glue supply means viatertiary glue supply means, in which the tertiary glue supply means areformed as a series of glue supply tubes, which are parallely arrangedand are at least almost of mutually equal dimensions.